German Patent No. 1,282,395 discloses a rotary slide valve of this type, which operates according to the counterflow principle, namely the infeed and outlet openings are provided at the same point, seen from the ceramic plates. This known rotary slide valve has a housing which has the infeed and outlet openings and contains the stationary ceramic disk. A member which can be rotated in this housing holds the other ceramic disk, fixed with respect to rotation relative to it. Furthermore a mixing chamber exists in the body of revolution. The two ceramic disks have the same shape. They each have a central, circular opening and two circular openings arranged on a circle which is concentric with respect to the central opening, the connecting line of said circular openings forming an acute angle. This rotary slide valve operates as follows:
Cold or hot water flows in through suitable openings in the housing and the openings of the stationary ceramic disk which coincide therewith. The body of revolution permits the adjustment of the two openings of the swivel plate mounted in said body of revolution with its outer openings relative to the stationary swivel plate in such a manner that starting with the complete covering of the two inflow openings first one can select from one liquid, for example first the cold one, a continuously increasing flow volume until the complete coincidence of both openings. Upon further rotation the cross section of this opening is again reduced, at the same time a suitable cross section of the second opening is freed, so that now the other liquid, for example the hot one, flows in in a suitable amount. The mixing relationship changes during further rotation until the first opening is covered and the second one is completely free. The second opening can subsequently be reduced until it is completely covered. This means that controlling the amount of liquid is possible with the two existing ceramic disks, however, a mixture flows independently from the mixing relationship totally all together always at the highest possible amount through the two disks. This liquid reaches the mixing chamber in the body of revolution and in the opposite direction of flow through the central openings of the two disks and an outlet opening in the housing to the outside. A control of the amount for a mixed liquid takes place outside of the rotary slide valve in a manner which is not discussed in detail. The known rotary slide valve is expensive in its structure, since its housing and the body of revolution may have only very small dimensional tolerances, if the operation is not supposed to be affected. Furthermore additionaal seals are required in the housing and the body of revolution. To control the outflow amount additional devices are required.
Furthermore Offenlegungsschrift No. 1 550 060 discloses a mixing valve, which contains in an expensive housing system two ceramic disks, the one of which rests rotatably and movably on the other one. The movable disk has thereby an approximately oval opening, which, depending on the position on the disk, releases certain cross sections of two inflow openings for cold and hot liquid of the stationary disk for the temperature adjustment and a certain cross section of an outlet opening of the stationary disk for volume regulation. Also this mixing valve operates according to the counterflow principle, whereby the hole of the movable disk is connected to a suitable mixing chamber. The entire device is extraordinarily expensive to manufacture, because many individual parts, sealing elements, etc., must be manufactured and assembled with an high exactness of fit. The same is true for a mixing valve according to Offenlegungsschrift No. 1 949 318 of the same Applicant, which operates according to the same principle with slightly different, but not less expensive, designs.
The purpose of the invention is to produce a mixing valve system of the above-discussed type, which can be manufactured simply and inexpensively, which is economical in operation and can easily be operated.